A sensor assembly may contain a structure provided with an optical fiber as a sensor element for detecting the amount of deformation in a vehicle body. The optical fiber is held between a bumper reinforcement and a bumper cover.
For example, in Japanese Laid-Open Patent Publication No. 2005-263038 (JP 2005-263038 A), when a load is applied to a bumper cover, the load is transmitted to the optical fiber by way of the bumper cover, and the optical fiber is deformed by the transmitted load. A pedestrian detection apparatus is disclosed in which the intensity of light passing through the interior of the optical fiber is altered by deformation of the optical fiber to detect that the vehicle body has collided with a pedestrian on the basis of the altered intensity of light.
However, in order to accurately detect impact with a pedestrian by using the detection apparatus of JP 2005-263038 A, the optical fiber must suitably deform in accordance with the load at the time of impact.
If the load at the time of impact is applied to an area away from the optical fiber, deformation may be brought about by the applied load at the position away from the optical fiber in the bumper cover.
If the deformed position comes into contact with the bumper reinforcement, the load will be transmitted directly to the bumper reinforcement from the bumper cover, and will not be efficiently transmitted to the optical fiber. For this reason, it is difficult to suitably deform the optical fiber (i.e., the sensor element) in accordance with the load at the time of impact and to accurately detect the load at the time of impact.